Charged hydrated soft tissues such as articular cartilage and the intervertebral disc have a strong tendency to swell in a hypotonic bath because of the high fixed charge density (FCD) within the tissue [e.g., 1–4]. For an excised tissue without externally applied loads, the tissue volume will change in response to changes in a bathing solution (free swelling) until the osmotic pressure is balanced by the elastic stresses on the solid matrix. A mechanical stress is needed to prevent the tissue from swelling from a given reference state (e.g., 0.15M NaCl). This stress may be called the swelling pressure relative to this reference state. The kinetic response of the swelling pressure to changes in bathing solution is associated with tissue material properties, such as the FCD, hydraulic permeability, ion diffusivity and stiffness of the solid matrix. In this study, we report our analysis on the one-dimensional confined swelling experiment of a charged hydrated soft tissue using the mechano-electrochemical theory developed in [3].

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